Pyrrolidinone derivatives have heretofore been known as drugs for cerebral insufficiency disease and so on. For instance, U.S. Pat. No. 4,369,139 discloses that 1-(p-methoxybenzoyl)-2-pyrrolidinone is useful in the prevention of cerebral insufficiency. European Patent 0 304 330 A1 discloses that 1-phenoxycarbonyl-2-pyrrolidinone is an intermediate for the preparation of carbamoylpyrrolidone derivatives which are useful as drugs for senile dementia, or as psychotropic and/or antiamnesia agents. However, said European patent gives no reference to the use as nootropic agents of 1-phenoxycarbonyl-2-pyrrolidinone and its derivatives having substituted phenyl.